Metal preparation and coatings made therefrom

ABSTRACT

The present invention is directed to metal preparations containing metal particles, in particular noble metal particles, to the use of such metal preparations for the production of attractive metallic decorative elements on articles having an outer silicatic surface such as of porcelain, ceramic, china, bone china, glass or enamel, to metallic coatings on such substrates and to a process for the production of coatings of this kind.

The present invention is directed to a metal preparation containing metal particles, in particular noble metal particles, to the use of such metal preparation for the production of attractive metallic decorative elements on articles having an outer silicatic surface such as of porcelain, ceramic, china, bone china, glass or enamel, to metallic coatings on such substrates and to a process for the production of coatings of this kind.

Decorative metallic coatings are highly desired for different consumer goods and architectural decorative elements. In particular, decorative elements colored with noble metals such as gold and silver apply the feeling of value and exclusivity to such goods.

In general, noble metal containing preparations for decorating glass, porcelain, china, bone cina, ceramics or similar surfaces consist of solutions of organic gold, organic palladium and/or organic platinum compounds being dissolved in appropriate organic carrier materials, of synthetic or natural resins as well as fluxes. Compositions of this kind exhibit a good adhesion to the respective substrate. Following their application to the substrate surface, the metal preparation is thermally treated and decomposes to the corresponding metal oxides and/or metals which adhere to the substrate and exhibit a glossy or matte visual impression of the surface decorations of gold or silver color depending on the starting compounds.

There are several methods known for the application of the metal preparations. Often, printing applications such as screen printing or tampon printing are used, but hand decoration by brush, stamping or by writing with a pencil is also still used.

The most common application process is screen printing. This process may be executed directly onto the surface of the silicate-type substrates as mentioned above, or may be executed in an indirect manner onto the surface of a transfer medium, from where it is transferred to the surface of the correspond-ding silicate-type substrate. Although the screen printing process is of advantage, there is a desire to allow the application of decorative noble metal effect coatings onto silicatic surfaces by application processes which are faster than screen printing, such as ink jet printing and other high-velocity printing processes. In addition, the use of noble metal compounds like organic palladium compounds and organic platinum compounds for the creation of silver colored effects is very expensive. Thus, there is also a need to replace palladium and platinum by metals which are more cost effective and lead to equally colored decorations.

Although silver compounds lend themselves to being used as starting material for the production of decorative silver effects on silicatic surfaces, the decomposition of organic silver compounds alone does not lead to shiny attractive silver colored decorations on silicatic surfaces, since the formation of defined metallic silver films or particles cannot be achieved without uncontrolled formation of dark silver oxide as an undesired by-product.

Furthermore, there have also been attempts to use noble metal particles in the corresponding metal preparations. Regarding noble metals such as gold, platinum or palladium, some applications of nano-sized metal particles in metal preparations could be found, e.g. for burnished gold.

For example, WO 2012/059088 A2 discloses a ceramic hot melt paint composition comprising nano-sized noble metal particles and at least one diffusion-inhibiting flow component.

US 2016/0236280 A1 discloses a process for the production of a layer structure which comprises nano-sized gold particles. They are used in a polar, protic organic solvent for the production of a shiny laminate structure at low temperatures. Thus, the coating of paper based substrates is possible, since the coating composition on the substrate only requires thermal treatment at a temperature in the range of from 25 to 200° C. A protective layer, if present, has to be applied in a second step after the application of the gold-containing coating composition onto the substrate and the heating thereof.

Since nano-sized silver particles corrode easily because of their high specific surface area, they have, thus far, not successfully been used for the production of decorative surface elements on silicatic surfaces.

Therefore, it is an object of the present invention to provide a metal preparation comprising metal particles, in particular nano-sized metal particles, preferably noble metal particles permitting the application of such metal preparation in a simple way by means of a broad range of printing or coating processes and leading in a one-step process to the production of highly decorative glossy metal elements on silicatic substrates which are mechanically stable, scratch resistant as well as corrosion resistant. It is a further object of the present invention to provide a metal preparation exhibiting the aforementioned advantages and comprising nano-sized silver particles as the sole metal particles wherein the metal preparation is designed such as to avoid corrosion of the silver particles. A still further object of the present invention is to show how such metal preparation may be used. An additional object of the present invention is to provide glossy, attractive decorative coatings on silicatic surfaces and a process for the production thereof.

In one embodiment (Embodiment I), the object of the present invention is solved by a metal preparation comprising

-   -   A) from 5 to 60% by weight of metal particles wherein said metal         particles         -   (i) exhibit a d₅₀ value, measured by the volume related             laser diffraction method, in the range of from 30 to 300 nm,         -   (ii) exhibit an average aspect ratio, measured by scanning             electron microscopy or transmission electron spectroscopy,             in the range of from 1.0 to 1.5, and         -   (iii) are selected from the group comprising Ag, Au, Ru, Ir,             Pd, Pt, Cu Nb, or an alloy comprising at least one thereof,     -   B) from 0.2 to 50% by weight of at least one organic compound of         one or more elements selected from the group comprising Si, Ge,         Nb, Sn, Zn, Zr, Ti, Sb, Al, Bi, alkali metal or alkaline earth         metal,     -   C) from 10 to 85% by weight of a solvent,     -   D) from 0.1 to 50% by weight of a polymeric binder,     -   E) 0.01 to 30% by weight of at least one metal compound, that is         soluble in organic solvent wherein the metal comprises at least         one from the group comprising Ag, Au, Ru, Ir, Pd, Pt, Os, and         Rh,

wherein the percentages are based on the total weight of the metal preparation.

In a further embodiment (Embodiment II), the object of the present invention is solved by a metal preparation comprising:

-   -   A) 5 to 40% by weight of metal particles exhibiting a d₅₀ value         in the range of from 30 to 300 nm, the d₅₀ value measured by the         volume related laser diffraction method, wherein the metal         particles are selected from the group comprising Ag, Au, Ru, Ir,         Pd, Pt, Cu, Nb, or of an alloy comprising at least one thereof,     -   B) 1 to 30% by weight of an organic compound of one or more         elements selected from the group comprising Si, Ge, Nb, Sn, Zn,         Zr, Ti, Sb, Al, Bi, alkali metal or alkaline earth metal, with         the proviso that at least an oxygen or nitrogen containing         organic compound of Si is present,     -   C) 10 to 70% by weight of a solvent, and     -   D) 5 to 25% by weight of a polymeric binder comprising at least         one compound selected from the group of polyvinylacetals,

wherein the percentages are based on the total weight of the metal preparation.

The object of the present invention is also solved by the use of the above described metal preparations as per Embodiments I and II for the manufacture of gold, platinum or silver colored decorative elements on articles exhibiting a surface such as porcellain, china, bone china, ceramic, glass or enamel.

In addition, the object of the present invention as per Embodiment I is solved by a metal particles containing solid coating on a substrate, comprising, based on the weight of the solid coating, at least 60%, preferably at least 80%, by weight of metal particles of at least one metal selected from the group consisting of Ag, Au, Ru, Ir, Pd, Pt, Cu, Nb, or an alloy containing at least one thereof, and further comprising at least 5% by weight, based on the total weight of the solid coating, of a glass matrix comprising at least one oxide of the group comprising SiO₂, GeO₂, B₂O₃, P₄O₁₀, NbO₂, Nb₂O₃, SnO, SnO₂, ZnO, ZrO₂, TiO₂, Al₂O₃, Bi₂O₃ and Sb₂O₃, alkali metal oxide, and/or alkaline earth metal oxide.

Analogously, the object of the present invention as per Embodiment II is solved by a metal particles containing solid coating on a substrate, comprising, based on the weight of the solid coating, at least 60%, preferably at least 80%, by weight of metal particles of at least one metal selected from the group consisting of Ag, Au, Ru, Ir, Pd, Pt, Cu, Nb, or an alloy containing at least one thereof, and further comprising at least 5% by weight, based on the total weight of the solid coating, of a glass matrix consisting of SiO₂ or a glass matrix comprising SiO₂ and at least one oxide of the group comprising GeO₂, NbO₂, Nb₂O₃, SnO, SnO₂, ZnO, ZrO₂, TiO₂, Al₂O₃, Bi₂O₃ and Sb₂O₃, alkali metal oxide, and/or alkaline earth metal oxide

Still furthermore, the object of the present invention is solved by a process for the production of a metal containing solid coating on a substrate, wherein a metal particles containing metal preparation as per Embodiments I or II is applied onto a substrate and is subsequently thermally treated at a temperature in the range of from 500° C. bis 1250° C.

The metal preparation according to Embodiment I contains as ingredient A 5 to 60% by weight, in particular 15 to 30% by weight, based on the total weight of the metal preparation of nano-sized metal particles exhibiting a d₅₃ value in the range of from 30 to 300 nm, preferably in the range of from 150 to 300 nm, wherein the d₅₀ value is measured by the volume related laser diffraction method according to ISO 13320:2009 wherein the metal particles are selected from the group comprising Ag, Au, Ru, Ir, Pd, Pt, Cu, Nb, or of an alloy comprising at least one thereof.

Further, the nano-sized metal particles of Embodiment I exhibit an average aspect ratio (AS), measured by scanning electron microscopy or transmission electron microscopy, in the range of from 1.5:1 to 1:1. Average aspect ratio (AS) of nano-sized metal particles, for the purposes of the present invention, shall mean their number aspect ratio mean as disclosed in a Technical Paper by A. Rawle of Malvern Instruments Limited titled “Basic Principles of Particle Size Analysis”, published e.g. as www.rci.rutqers.edu/˜moghe/PSD %20Basics.pdf. For the purposes of the present invention, AS of particles is determined (i) by providing a 2-D projection of such particles under the scanning electron microscope (SEM) or transition electron microscope (TEM), (ii) measuring the maximum (d₁) and minimum (d₂) length of 50 to 100 individual particles, (iii) forming the aspect ratio d₁:d₂ of individual particles, and (vi) forming the average aspect ratio AS by summing all individual aspect ratios and dividing by the number of particles. The average aspect ratio AS is provided in the form AS=a:1, i.e. normalized to the smaller diameter as 1.

The metal preparation according to Embodiment II contains as ingredient A 5 to 40% by weight, in particular 15 to 30% by weight, based on the total weight of the metal preparation of nano-sized metal particles exhibiting a d₅₀ value in the range of from 30 to 300 nm, preferably in the range of from 150 to 300 nm, wherein the d₅₀ value is measured by the volume related laser diffraction method according to ISO 13320:2009 wherein the metal particles are selected from the group comprising Ag, Au, Ru, Ir, Pd, Pt, Cu, Nb, or of an alloy comprising at least one thereof.

The metal preparations may comprise only one kind of metal particles or a mixture of two or more kinds of metal particles.

Preferably, the nano-sized metal particles are noble metal particles, wherein the noble metals are selected from the group comprising Ag, Au, Ru, Ir, Pd and Pt, or an alloy comprising at least one thereof. Most preferred, the nano-particles are of silver or a silver alloy containing at least 50% by weight, based on the total weight of the alloy, of silver.

It is a great advantage of the present invention that metal preparations containing solely silver nano-sized particles and no further metal particles are corrosion resistant for a time period of several months. Such metal preparations may be used for the production of corrosion resistant glossy silver colored decorative elements on silicatic surfaces.

In addition to the nano-sized metal particles, the metal preparation as per Embodiment I of the present invention further comprises, as ingredient B, 0.2 to 50% by weight, in particular 1-15% by weight, based on the total weight of the metal preparation, of an organic compound of one or more elements selected from the group comprising Si, Ge, B, P, Nb, Sn, Zn, Zr, Ti, Sb, Al, Bi, alkali metal and alkaline earth metal.

In addition to the nano-sized metal particles, the metal preparation as per Embodiment II of the present invention further comprises, as ingredient B, 1 to 30% by weight, in particular 2-20% by weight, based on the total weight of the metal preparation, of an organic compound of one or more elements selected from the group comprising Si, Ge, Nb, Sn, Zn, Zr, Ti, Sb, Al, Bi, alkali metal and alkaline earth metal, with the proviso that at least an oxygen or nitrogen containing organic compound of Si is present.

Said organic compound(s) as per ingredient B act as a glass former in the resulting solid coating on a substrate, since they decompose upon thermal treatment to the corresponding metal oxides.

One component of ingredient B may be an oxygen or nitrogen containing organic silicon compound which has to be present according to the invention of Embodiment II. Such organic silicon compound may be present in the metal preparation of the present invention as the sole organic compound, but may also be present in combination with one or more further organic compounds of Ge, Nb, Sn, Zn, Zr, Ti, Sb, Al, Bi, alkali metal and alkaline earth metal. The organic silicon compound may be completely absent in the metal preparations of Embodiment I. If present, the oxygen or nitrogen containing organic silicon compound forms a Si—O-based network upon thermal decomposition in an oxygen containing atmosphere. In order to be useful for the present purpose, the corresponding oxygen or nitrogen containing organic silicon compound must not evaporate prior to its decomposition. Silicon comprising polymers such as polysilazane compounds, polysiloxane compounds and silicone resins of general Formula 1, Formula 2 or Formula 3 are particularly useful as oxygen or nitrogen containing organic silicon compound B.

wherein

-   R¹ is a radical selected from the group consisting of H, C₁-C₁₈     alkyl, C₅-C₆ cycloalkyl, substituted or non-substituted phenyl, OH,     OC₁-C₁₈ alkyl, NH₂ and N(C₁-C₁₈ alkyl)₂; -   R², R³ and R⁵ is, independently from each other, a radical selected     from the group consisting of H, C₁-C₁₈ alkyl, OH, OC₁-C₁₈ alkyl,     NH₂, N(C₁-C₁₈ alkyl)₂, OSi(R¹)₃ and N═SiR¹; -   R⁴ is a radical selected from the group consisting of H, C₁-C₁₈     alkyl, C₅-C₆ cycloalkyl and phenyl; -   X is a radical of O or N; and -   m and n is, independently from each other, an integer selected from     the numbers in the range of from 1 to 100,

with the proviso that the boiling point of each of the resins according to Formulae 1-3 is exceeding 150° C.

For example, Durazan 1066 (CAS-No. 346577-55-7) or polydimethylsiloxane (CAS-No. 9016-00-6) may advantageously be used as oxygen or nitrogen containing organic silicon compound B) in the present metal preparation.

In addition, silsesquioxane polymers of general Formula 4 are advantageously useful as well:

wherein

-   R¹ and R² are radicals equal or different from each other and are     selected from the group consisting of hydrogen, alkyl, cycloalkyl,     aryl, and alkoxyl, and -   m and n is, independently from each other, an integer selected from     the numbers in the range of from 1 to 100,

with the proviso that the boiling point of each of the silsesquioxane polymers is exceeding 150° C.

Further silicon comprising polymers that are suitable as ingredient B include silicone-modified alkyd resins and silicone-polyester resins.

Furthermore, in addition to or in the absence of an oxygen or nitrogen containing organic silicon compound, the metal preparation of Embodiment I of the present invention may comprise as ingredient B organic compounds of elements selected from the group comprising Ge, B, P, Nb, Sn, Zn, Zr, Ti, Sb, Al, Bi, alkali metal and/or alkaline earth metal.

Organic compounds of elements selected from the group comprising Si, Ge, B, P, Nb, Sn, Zn, Zr, Ti, Sb, Al, Bi, alkali metal and/or alkaline earth metal may include alcoholates, carboxylates, citrates, acetylacetonates and/or tartrates of the corresponding elements. They are present, if at all, in an amount of from 1 to 30% by weight, based on the total weight of the compounds of ingredient B, in the metal preparation as per Embodiment I. The content of organic alkali metal compound and/or organic alkaline earth metal compound should not exceed 10% by weight, based on the total weight of the compounds of ingredient B.

In addition to an oxygen or nitrogen containing organic silicon compound, the metal preparation of Embodiment II of the present invention may comprise as ingredient B organic compounds of elements selected from the group comprising Ge, Nb, Sn, Zn, Zr, Ti, Sb, Al, Bi, alkali metal and/or alkaline earth metal. Organic compounds of elements selected from the group comprising Si, Ge, Nb, Sn, Zn, Zr, Ti, Sb, Al, Bi, alkali metal and/or alkaline earth metal may include alcoholates, carboxylates, citrates, acetylacetonates and/or tartrates of the corresponding elements. They are present, if at all, in an amount of from 1 to 30% by weight, based on the total weight of the compounds of ingredient B, in the metal preparation as per Embodiment II. The content of organic alkali metal compound and/or organic alkaline earth metal compound should not exceed 10% by weight, based on the total weight of the compounds of ingredient B.

Preferably, alcoholates of Si, Ge, B, P, Nb, Sn, Zn, Zr, Ti, Sb, Al, Bi, alkali metal and alkaline earth metal are found suitable. Also, carbonic acid, sulfonic acid and/or sulfinic acid salts of Formula 5 are found suitable:

wherein

-   Met is selected from the group consisting of Si, Ge, B, P, Nb, Sn,     Zr, Ti, Sb, Al, Bi, alkali metal and alkaline earth metal; -   Z is selected from the group consisting of CO, SO, and SO₂, -   p is 0 or 1, -   q is 1 to 4 -   R⁶ is a radical selected from the group consisting of C₁-C₁₈ alkyl,     C₅-C₆ cycloalkyl and substituted or non-substituted phenyl.

The metal preparation of Embodiment I of the present invention further comprises, as ingredient C, 10 to 85%, preferably 40 to 70%, by weight of a solvent, based on the total weight of the metal preparation.

The metal preparation of Embodiment II of the present invention further comprises, as ingredient C, 10 to 70%, preferably 20 to 76%, by weight of a solvent, based on the total weight of the metal preparation

The solvent of Embodiments I or II is advantageously an organic solvent. The organic solvent used in the present metal preparation may have a water content of from 0 to at most 10% by weight, based on the weight of the solvent. In the event that mixtures of organic solvents are used, which is preferred, each of the organic solvents may have a water content in the range of from 0 to at most 10% by weight, based on the weight of each organic solvent, such that the maximum amount of water in the solvent mixture does not exceed 10% by weight. For the single organic solvent or the mixture of organic solvents, as the case may be, the water content is preferably from 0 to 5% by weight, more preferably from 0 to 3% by weight, for each single organic solvent used.

In principle, all organic solvents which are capable of dissolving the solid compounds (except the metal particles) and evaporate without residue at the temperature of the thermal treatment of the resulting coating layer on the silicatic substrate may be used in the present metal preparation. Examples of suitable solvents are at least one of the group comprising alcohols, aromatic solvents, ketones, esters, ethers, ether-alcohols, saturated and unsaturated aliphatic hydrocarbons, or amides. Suitable alcohols are ethanol, isopropanol, hexanol or 2-ethylhexanol, ethoxyethanol, methoxyethanol, methoxypropanol and mixtures thereof. In addition, ethers of polyalcohols are particularly useful, especially tri-propyleneglycol-monomethylether (TPM) and di-propyleneglycol-monomethylether (DPM). Most preferred are 2-ethylhexanol, tri-propyleneglycol-monomethylether (TPM) and di-propyleneglycol-monomethylether (DPM). All solvents may be used as sole solvent or in a mixture containing several solvents.

Optionally, non-alcoholic solvents may also be present in the solvent mixture, for example, but not limited to ethers like dialkylpropyleneglycols, dioxane or THF, aromatic solvents like xylenes, saturated and non-saturated aliphatic hydrocarbons like terpenoic solvents and naphtha, amides like M-ethylpyrrolidone, esters like ethyl benzoate or fatty acid esters, in an amount of from 1 to up to 40% by weight, based on the weight of the solvent mixture.

By varying the amount of the solvent, the viscosity of the metal preparation according to the present invention may be adapted to a value which is useful and appropriate in the applicable coating or printing technique. It is a great advantage of the present invention that the metal preparation may be used in several coating or printing techniques by which a concentrated metal preparation may be produced which may be diluted up to the requested value by simply adapting the content of the solvent and is, thus, useful for several coating or printing techniques including ink jet printing.

The metal preparation according to Embodiment I of the present invention further comprises, as ingredient D, from 0.1 to 50% by weight, preferably 10 to 42% by weight, based on the total weight of the metal preparation, of a polymeric binder.

The metal preparation according to Embodiment II of the present invention further comprises, as ingredient D, from 5 to 25% by weight, preferably 10 to 20% by weight, based on the total weight of the metal preparation, of a polymeric binder comprising at least one compound selected from the group of polyvinylacetals.

The binder contributes to determine the viscosity of the metal preparation during the printing process. Although the metal preparation has to be of a viscosity low enough to be printable or coatable in various printing or coating processes, the respective coating or printing layer, once applied, must remain stable on the substrate without distributing beyond the coated surface area. In addition, the binder must burn completely upon thermal treatment of the resulting coating or printing layer in the application field of the present metal preparation.

As the binder of metal preparations according to Embodiment I, it is possible to use, for example, celluloses, polyamides, polyesters, polyvinyls, polyacetals, polyvinylacetals, polysulfone, phenolic resin, ketone resin, epoxy resin, maleic resin, and rosin resin.

Polymeric binders which contain at least one compound selected from the group of polyvinylacetals advantageously serve for the purpose of providing a metal preparation according to Embodiment II to be used in printing and coating processes. Polyvinylacetals may be polyvinylformal, polyvinylacetaldehyde and polyvinylbutyral.

The characteristics of polyvinylacetals vary with their degree of acetalization. Among polyvinylacetals, polyvinylbutyrals turned out to be the best choice for the metal preparations of the present invention. Therefore, polyvinylbutyrals are preferably used as the polyvinylacetal type binder in the present metal preparations. Especially useful are polyvinylbutyrals with an OH content of from 18 to 21% by weight.

Polyvinylbutyrals from Kuraray, which are sold under the registered trademarks Mowital® and Pioloform® may advantageously be used, in particular Mowital® B 45 H and Mowital® B 60 H which have an average molar mass of about 40.000 g/mol and about 55.000 g/mol, respectively, and each exhibit a glass transition temperature of about 70° C. Mowital® B 60 H is preferred. It goes without saying that polyvinylbutyrals of further companies having comparable characteristics are useful as well.

The polyvinylacetal containing binder may contain the polyvinylacetal to at least 50% by weight, based on the total weight of the binder, or may consist of at least one compound selected from the group of polyvinylacetals. Preferably, the binder comprises polyvinylbutyral. In the most preferred embodiment of the present invention, the binder consists of polyvinylbutyral.

Most preferred, the binder consists of a polyvinylburtyral having an average molar mass in the range of from 30,000 to 60,000 g/mol and an OH content of from 18 to 24% by weight.

The metal preparation according to Embodiment I of the present invention further comprises, as ingredient E, from 0.01 to 30% by weight of at least one metal compound that is soluble in organic solvent wherein the metal comprises at least one from the group comprising Ag, Au, Ru, Ir, Pd, Pt, Os, and Rh.

The metal preparation according to Embodiment II of the present invention optionally comprises, as ingredient E, from 0 to 5% by weight of at least one metal compound that is soluble in organic solvent wherein the metal comprises at least one from the group comprising Ag, Au, Ru, Ir, Pd, Pt, Os, and Rh.

Metal compound E serves for the adaption of the color of the resulting metal layer in the resulting coated product, and/or facilitating the adherence of the respective metal preparation to the substrate in the subsequent coating procedure. It is decomposed under the final thermal treatment of the metal preparation on the coated substrate to the corresponding metal oxide and/or metal.

Preferably, organic metal salts are used as ingredient E in the metal preparation according to the present invention. Examples are resinates, sulforesinates, thiolates, carboxylates and alcoholates of the aforementioned elements. The organic metal salts are usually used as a solution thereof in any of the organic solvents specified as ingredient C.

The metal preparations according to the present invention may further comprise, as ingredient F, from 0 to 5% by weight of at least one metal compound wherein the metal comprises at least one from the group comprising Co, Ni, Cu, Cr, Fe, and Mn.

Metal compound F serves for further adaption of the color of the resulting metal layer in the resulting coated product. It is decomposed under the final thermal treatment of the metal preparation on the coated substrate to the corresponding metal oxide and/or metal.

Preferably, organic metal salts are used as ingredient F in the metal preparation according to the present invention. Examples are resinates, sulforesinates, thiolates, carboxylates and alcoholates of the aforementioned elements. The organic metal salts are usually used as a solution thereof in any of the organic solvents specified as component C.

In addition to mandatory ingredients A-E of Embodiment I or A-D of Embodiment II, and optional ingredient F of Embodiment I and optional ingredients E and F of Embodiment II, the metal preparations of the present invention may further optionally comprise, as ingredient G, a rheology modifying agent in case that the viscosity of the metal preparation has to be adapted further in a very particular manner. The rheology modifying agent may be present in an amount of from 0 to 10% by weight, based on the total weight of the metal preparation. Preferably, an amount of from 0 to 8% by weight, in particular of from 0 to 5% by weight, is being used. The rheology modifying agent used in the present metal preparation may be selected from the group consisting of pine oil, castor oil, a fatty acid, a fatty acid derivative and a natural or synthetic wax.

Examples for fatty acids are linoleic acid, oleic acid, stearic acid, palmitic acid, myristic acid, lauric acid and capric acid. Derivatives thereof are useful as well.

Examples for natural and synthetic waxes are montane waxes of C₁₉ to C₃₀ hydrocarbons, canauba wax, tan waxes, collophonium waxes like abietic acid or rosin, or polyolefin waxes like Ceridust® waxes of Clariant, to name only a few.

Still furthermore, the metal preparations of Embodiments I or II according to the present invention may also optionally comprise, as ingredient H, from 0 to 10% by weight, based on the total weight of the metal preparation, of a dispersant.

The dispersant includes at least one of the following: (i) a non-surface active polymer or (ii) a surface-active substance. The dispersant serves to improve the separation of metal particles and to prevent settling or agglomeration.

There is a wide range of non-surface active polymers that may act as effective dispersants, such as e.g. polyacrylic acid, polyacrylates and their copolymers, polyurethanes, and polyvinylpyrrolidone. Non-surface active polymers used as a dispersant differ from the polymers used as polymeric binders (ingredient D).

In the present invention, polyvinylpyrrolidone is preferred as the non-surface-active polymer dispersant.

The surface-active substance (ii) can be selected from the group consisting of a nonionic surfactant, an anionic surfactant, a cationic surfactant and an amphoteric surfactant and mixtures of at least two thereof. All the surfactants mentioned comprise a nonpolar part and a polar part. The nonpolar part can be selected from groups including branched, linear, or aromatic groups such as an alkyl group, an alkyl benzene group and combinations thereof. The polar part of the nonionic surfactants can be selected from the group consisting of an alcohol group, an ether group, an ester group, an amide group, an acrylate group and combinations of at least two thereof. The polar part of the anionic surfactant can be selected from the group consisting of a carboxylate, a sulfonate, a sulfate, a phosphate and mixtures of at least two thereof. The polar part of the cationic surfactant can, for example, be an, optionally substituted, ammonium group. The polar part of the amphoteric surfactant can be selected from combinations of at least one polar part of a cationic surfactant and an anionic surfactant.

Exemplary nonionic surfactants include: long-chain aliphatic alcohols, ethoxylated aliphatic alcohols (such as octaethylene glycol monododecyl ether or pentaethylene glycol monododecyl ether), polypropylene glycol alkyl ethers, glucoside alkyl ethers, polyethylene glycol octylphenyl ethers (such as Triton X-100), polyethylene glycol alkylphenyl ethers, glycerol alkyl esters, polyoxyethylene glycol sorbitan alkyl esters, sorbitan alkyl esters, cocamide MEA, cocamide DEA, dodecyldimethylamine oxide, polyethoxylated tallow amine carboxylic esters, polyethylene glycol esters, glycol esters of fatty acids, carboxylic amides, monoalkanolamine condensates, or polyoxyethylene fatty acid amides.

Exemplary anionic surfactants include: alkyl carboxylates (such as sodium stearate), alkyl sulfates, alkylbenzene sulfonates, naphthalene sulfonates, olefin sulfonates, alkyl sulfonates, sulfated natural oils, natural oils and fats, sulfated esters, sulfates alkanol amides, ethoxylated and sulfated alkyl phenols. Prominent alkyl sulfates include ammonium lauryl sulfate, sodium lauryl sulfate (“SLS”, or “SDS”), and the related alkyl-ether sulfates sodium laureth sulfate (“SLES”), and sodium myreth sulfate. Others include: dioctyl sodium sulfosuccinate, perfluorooctane sulfonate, perfluorobutane sulfonate, alkyl-aryl ether phosphates, alkyl ether phosphates, phosphates of ethoxylated aliphatic alcohols. More specialized carboxylates include sodium lauroyl sarcosinate and carboxylate-based fluorosurfactants such as perfluoro nonanoate or perfluorooctanoate (“PFOA” or “PFO”).

Exemplary cationic surfactants include: pH-dependent primary, secondary, or tertiary amines, and their ammonium salts, including quaternary ammonium salts. Permanently charged quaternary ammonium salts include: Cetrimonium bromide, cetylpyridinium chloride, benzalkonium chloride, benzethonium chloride, dimethyldioctadecylammonium chloride, dioctadecyldimethylammonium bromide, amines with amide linkages, polyoxyethylene alkyl & alicyclic amines; N,N,N′,N′ tetrakis substituted ethylene diamines and 2-alkyl 1-hydroxyethyl 2-imidazolines.

The cationic part of amphoteric surfactants is based on primary, secondary, or tertiary amines or quaternary ammonium cations. The anionic part can be more variable and include sulfonates, as in the sultaines CHAPS (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate) and cocamidopropyl hydroxysultaine. Betaines such as cocamidopropyl betaine have a carboxylate with the ammonium. The most common biological zwitterionic surfactants have a phosphate anion with an amine or ammonium, such as the phospholipids phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, and sphingomyelins.

In the present invention, the use of anionic surfactants, such phosphates of ethoxylated aliphatic alcohols, is preferred.

Furthermore, the metal preparations of Embodiments I or II according to the present invention may optionally comprise, as ingredient I, at least one additive which is usually used for the production of metallic coatings on silicatic substrates, such as surface active agents, defoaming agents, organic pigments and fillers, further thixotropic agents and the like. If such additives are used, their weight percentage is chosen such that the total of all ingredients A) to I) adds to 100% by weight.

It goes without saying that that all weight percentages mentioned above, unless noted otherwise, refer to the total weight of the metal preparation.

The present invention is also directed to a process for the production of the metal preparations of Embodiments I or II which is characterized in that mandatory and optional ingredients are intimately mixed with each other to obtain a ready-to-use metal preparation. Preferably, a solution of the polymeric binder (ingredient D) is prepared and the other ingredients, preferably mixed with one or more of the solvents, are added successively thereto. If desired or necessary, one or more of the further additives mentioned above may be added as well. The mixing is preferably carried out by a rotor-stator-homogenizer or by a Speedmixer® at ambient temperature. In some cases, deaeration may be of importance, depending on the amount and the kind of the solvent used.

It is a great advantage of the present invention that the process for the production of the metal preparations of Embodiments I or II is as simple as possible. The mere mixing of the ingredients is sufficient to arrive at a stable metal preparation which has a shelf life of and may be stored in closed containers for at least six months without degradation, decomposition or settling of the solid ingredients. Depending on the content of solvents, rheology modifying agents and/or other thixotropic agents, the metal preparations may be used in various coating or printing processes including ink jet printing. Therefore, a concentrated form of the present metal preparations may serve the customer for the application thereof in several coating or printing processes, since the content of the solvent may also be adjusted at a later point of time at the customer's site.

The present invention is also directed to the use of the metal preparations of Embodiments I or II for the manufacture of gold, platinum or silver colored decorative elements on articles exhibiting a surface such as porcelain, china, bone china, ceramic, glass or enamel.

To arrive at such metallic elements on silicatic surfaces as mentioned above, the metal preparations of Embodiments I or II must be applied to a surface of an article and subsequently treated further.

Therefore, the present invention is also directed to a process for the production of a metal containing coating on a substrate, wherein a metal preparation of Embodiment I or II is applied onto the substrate and subsequently treated at a temperature in the range of from 500° C. to 1250° C. The treatment is executed in an oxygen containing atmosphere.

The substrate having the said silicatic surface is, according to the present invention, an article exhibiting a surface of porcelain, china, bone china, ceramic, glass or enamel. The kind of the article is not limited per se. In principle, all articles which may be enriched in decor or function by having a metallic layer of the metals mentioned as ingredient A of the metal preparations of Embodiments I or II on their surface may be used. Examples are tiles, architectural elements, glasses and china for household or professional application, and the like.

The metal preparations of Embodiments I or II may be applied onto the surface of the substrate either directly or by means of a transfer medium.

Direct application can take place by any process which is known to the skilled person in the field. The metal preparations of Embodiments I or II can be applied onto the substrate by dipping the substrate into the applicable metal preparation or by any coating or printing process, such as curtain coating, roller coating, spin coating, impregnation, pouring, dripping-on, squirting, spraying-on, doctor blade coating, painting or printing, whereby the printing may be an ink jet printing, screen printing, gravure printing, offset printing or pad printing process and the painting process is a pencil painting, brush painting or the like process.

The coating process is chosen dependent upon the kind of substrate and the size and kind of coating which is to be applied onto the substrate. It goes with out saying that the viscosity of the metal preparations of Embodiments I or II has to be adapted to the required coating technique. Since the viscosity of the present metal preparations is adjustable, in most cases simply by altering the amount of the respective solvent(s), a concentrated metal preparation according to the present invention may be used as base composition for use in more than one application technique.

Preferred printing processes are screen printing, gravure printing, pad printing and ink jet printing. Painting by means of a brush or pencil can also advantageously be used.

The application of the metal preparations of Embodiments I or II onto the substrate may also be conducted employing an indirect process, i.e. by applying the applicable metal preparation onto a transfer medium in a first step, and applying, in a second step, the metal preparation to the substrate by means of the transfer medium which is pre-coated with a metal preparation according to the present invention. Herein, the metal preparation may be applied onto the transfer medium via a printing process, such as thermoplastic screen printing, ink jet printing, tampon printing, or offset printing.

The transfer medium may be composed of a polymer or paper carrier, e.g. in form of a decalcomania which is pre-coated with a metal preparation of Embodiments I or II and dried. The metal preparation is then applied to the substrate by positioning the pre-coated carrier on the substrate and removing the polymer or paper carrier. The thermal treatment is executed in this case after application of the metal preparation onto the substrate, not after application of the metal preparation on the polymer or paper carrier.

The substrate may have any shape which allows the application of the applicable metal preparation to the substrate. Flat, two dimensional substrates such as films, plates and sheets are equally useful as three-dimensional substrates of any shape like a sphere or a cone, or any other useful three-dimensional shape. The substrate may be a compact or hollow body having an outer and/or inner silicatic surface of porcelain, china, bone china, ceramic, glass or enamel which is to be covered by a metal preparation of the present invention.

The silicatic surface of the substrate preferably comprises at least one continuous area onto which the metal preparation of Embodiments I or II may be applied. The area covered by the metal preparation may have any appropriate shape, in the form of regular or irregular patterns, lines, geometric shapes such as circles, squares, rectangles and the like, photographs, logos, bar codes, etc. Size and shape of the substrate area covered by the metal preparation are limited merely by the kind of the coating or printing process used and/or by the geometrical shape of the substrate itself. The present coating process allows the manufacturing of patterns having very fine line diameters of about 0.05 mm on the substrate.

The size of the coated area is in the range of from 0.5 mm² to 10 m², in particular from 10 mm² to 5 m², and most preferred in the range of from 100 mm² to 1 m². Line diameters of from 0.01 mm to 10 cm, in particular of from 0.1 mm to 1 cm, are possible as well.

Conducting the coating process and thermally treating the applied layer according to the present invention yields a solid coating layer on the substrate, wherein the coating layer contains a continuous compact metallic layer comprising nano-sized metal particles as per ingredient A of the metal preparations, wherein the nano-sized metal particles are at least partly enveloped by a glassy matrix.

According to the present invention, the composition and process are selected such that during the thermal treatment step said continuous compact metallic layer is being covered by a glassy top coat. The glassy matrix as well as the glassy top coat contain oxides of the metals mentioned under ingredient B and, mandatorily or optionally, metals or oxides of the metals of ingredients E and F, respectively. In case of Embodiment II, the glassy matrix and the glassy top coat at least contain a network composed of silicon and oxygen atoms. Residual nitrogen atoms may be present as well.

The resulting glassy top coat protects the metallic layer and prevents corrosion and/or mechanical or chemical decomposition thereof, whereas the matrix enveloping the metal particles enables the adherence of the nano-sized metal particles to the substrate.

Although the metal preparations according to the present invention, having been applied to the substrate and thermally treated, automatically generate a top coat which protects the metallic layer as explained above, it might be desired or of advantage to cover the resulting solid coating layer by one or more further protective layers (P). Therefore, the present process optionally also includes a process step wherein the coating layer obtained from a metal preparation of Embodiments I or II may be further partly or fully covered with an additional protective layer (P). This process step may be executed prior to the thermal treatment of the then resulting layer stack or even after the execution of the thermal treatment of the coating layer obtained by coating the metal preparation onto the substrate.

The present invention is also directed to a metal particles containing solid coating on a substrate, comprising, based on the weight of the solid coating, at least 60% by weight, preferably at least 80% by weight, of metal particles of at least one metal, selected from the group comprising Ag, Au, Ru, Ir, Pd, Pt, Cu, Nb, or an alloy comprising at least one thereof, and comprising at least 5% by weight, based on the weight of the solid coating, of a glass matrix comprising, in case of Embodiment I, at least one oxide of the group comprising SiO₂, GeO₂, B₂O₃, P₄O₁₀, NbO₂, Nb₂O₃, SnO, Sn₀₂, ZnO, ZrO₂, TiO₂, Al₂O₃, Bi₂O₃, Sb₂O₃ and alkali metal oxide, and/or alkaline earth metal oxide; or in case of Embodiment II, either consisting of SiO₂, or comprising SiO₂ and at least one oxide of the group comprising GeO₂, NbO₂, Nb₂O₃, SnO, SnO₂, ZnO, ZrO₂, TiO₂, Al₂O₃, Bi₂O₃, Sb₂O₃ and alkali metal oxide, and/or alkaline earth metal oxide.

The metal particles are the nano-sized metal particles of ingredient A as already described above with respect to the metal preparations.

The content of the glass matrix is preferably in the range of from 5 to 40% by weight, in particular of from 10 to 30% by weight, based on the weight of the solid coating. Thus, the content of the metal particles in the metal particles containing solid coating on the substrate is preferably at least 60% by weight, most preferably in the range of from 80 to 95% by weight of the total weight of the solid coating.

It is of advantage that the glass matrix contains alkali metal oxides and/or alkaline earth metal oxides up to a percentage of at most 5% by weight, based on the weight of the solid coating on the substrate, because alkali metal oxides and/or alkaline earth metal oxides in such a low concentration may improve the mechanical characteristics of the resulting coating with respect to scratch resistance and durability in long-term exposure to steam.

The decomposition products of the metal salt(s) according to ingredient E and, if present, ingredient F of the metal preparation count on the glass matrix content rather than counting on the metal particles content. Therefore, the glass matrix may also additionally contain one or more metals or metal oxides, the metal selected from the group Ag, Au, Ru, Ir, Pd, Os, Pt, Rh, Co, Ni, Cu, Cr, Fe and Mn.

Preferably, the glass matrix contains metals selected from Au, Rh and/or Ru, derived from the compounds of ingredient E.

In a preferred embodiment of the present invention, the metal particles in the metal particles containing solid coating on the substrate are composed of one or more noble metals selected from the group consisting of Ag, Au, Ru, Ir, Pd, Pt, or an alloy comprising at least one thereof.

Most preferred is the embodiment, wherein the solid coating on a substrate merely contains particles of silver or a silver containing alloy having a silver content of at least 50% by weight, based on the weight of the alloy.

As already explained above, the metal particles containing solid coating on a substrate is composed of two layers lying on top of each other, wherein a first layer is located directly on the substrate and constitutes a densely packed metallic layer comprising aggregated metal particles and wherein the second layer is located on top of the first layer and is a glass-like layer comprising oxides of elements of ingredients B, and optionally F.

The densely packed metallic layer constitutes a continuous layer wherein the metal particles are still recognizable as particles exhibiting a d₅₀ value in the range of from 30 to 300 nm, but are aggregated and partly fused together and are, at least partly, enveloped by a glassy matrix which is composed of the same ingredients as the glass-like layer on top of the metallic layer.

The optional protective layer (P) which has a glass-like structure is either composed of a glass matrix comprising SiO₂ alone or SiO₂ and at least one metal oxide selected from the group of alkali metal oxides, alkaline earth metal oxides, GeO₂, NbO₂, Nb₂O₃, SnO, SnO₂, ZnO, ZrO₂, TiO₂, Al₂O₃, Bi₂O₃ and Sb₂O₃ and is formed from aqueous or non-aqueous precursors of said oxides. Aqueous precursors are selected from the group of alkaline solutions, e.g. sodium or potassium orthosilicate as a precursor of SiO₂, or suspensions of hydroxide particles in alkaline solutions, e.g. aluminum hydroxide particles in solutions of sodium or potassium orthosilicate. Non-aqueous precursors are selected from the group of metal alkoxylates or metal carboxylates and can optionally be provided in solvents or in combination with resins. Resins may include the polymeric binders disclosed herein as ingredient D. SiO₂-precursors can be also selected from the group of materials characterized by Formulae 1, 2, 3 or 4 herein above. The optional protective layer (P) may be applied before or after thermal treatment of the particle containing layer and is located on top of the automatically generated top coat.

In a most preferred embodiment of the invention, the solid coating on the substrate, according to the present invention, is composed of a metallic layer which comprises particles of silver or an alloy having a silver content of at least 50% by weight, based on the weight of the alloy, exhibiting a d₅₀ value in the range of from 30 to 300 nm as described above, which is located directly on the substrate, and a protective layer (P) on top of the metallic layer wherein said layer (P) comprises SiO₂ and rhodium. The amount of metal (i.e. Ag or an alloy comprising Ag) is at least 80% by weight, the amount of SiO₂ at least 3% by weight and the amount of rhodium at most 0.5% by weight, based on the total weight of the coating.

The protective layer (P) as described above provides additional protection of the metallic layer against corrosion and chemical decomposition, particularly if silver particles are employed. Such protection may be required if the resulting decorative layer is intended to be exposed to reactive, in particular sulfur compounds containing, environments. In addition, it provides an improved scratch resistance to the subjacent metallic layer if excessive mechanical stress to the decorative layer is expected.

The substrate whereon the solid coating layer is located is an article exhibiting an outer silicatic surface which is a surface of, for example, porcelain, china, bone china, ceramic, glass or enamel. It goes without saying that the whole article may be composed of one of the materials mentioned above, but articles which merely have a silicatic surface, wherein the body of the article is composed of a different material, shall also be included in the present invention. Of course, the surface of the article as well as the body thereof must withstand the temperature of thermal treatment at 500-1250° C. Shape and size of the article itself are not limited. The silicatic surface may either be an outer surface or an inner surface of the article (e.g. for hollow articles).

The present invention allows the coating of silicatic surfaces of articles in one coating step with a glossy or matte, as the case may be, metallic layer which exhibits a silver or golden color and is protected against chemical or mechanical decomposition or corrosion. Even the metal preparations of Embodiments I and II themselves have a long shelf life, i.e. bearing resistance against corrosion and decomposition for at least six months. The nano-sized metal particles used may be produced prior to use in an appropriate size and do not have to be produced in situ on the surface to be covered, as it is state of the art for making gold decorations on silicatic surfaces. Since even nano-sized silver particles are stable enough against corrosion in the present metal preparations the use of silver instead of palladium and platinum is possible for the production of silver colored decorations on silicatic articles such as pottery, glasses and tiles for personal or industrial use, leading to an improved cost control in the production of the respective goods.

The present invention shall be explained in detail in the following examples, although it shall not be restricted thereto.

EXAMPLES

Method for the Determination of the Average Aspect Ratio of an Assemble of Metal Particles

A representative SEM or TEM image of metal particles as shown in FIG. 1 containing m=50 to m=100 countable particles is subjected to the following procedure:

Every diameter of a particle is measured at the longest position to yield a value d₁. The perpendicular diameter to this position is measured as well to yield a value d₂.

The aspect ratio AS is determined by the following formula considering the aspect ratio d₁:d₂ for every particle independent of its size:

${AS} = {\sum\limits_{n = 1}^{m}{\left( {d_{1}\text{:}d_{2}} \right)\text{:}\mspace{11mu} m}}$

The average aspect ratio AS is provided in the form AS=a:1, i.e. normalized to the smaller diameter as 1.

Example A—Suitable Metal Particles for a Composition According to this Invention

Silver particles were prepared according to US20130270490 A1, example 1 and subsequently converted to a tripropylene glycol monomethylether-based formulation according to example 10 of the same publication (50% solids content).

The resulting silver particles were filtered off, washed with ethanol, dried and subjected to SEM analysis providing an aspect ratio of 1.15:1 at a d₅₀ of 70 nm, d₉₀ of 115 nm (see FIG. 1).

Comparative Example B—Unsuitable Metal Particles for a Composition According to this Invention

Silver particles were prepared according to the methods described in Sabrina Daumann's doctorate dissertation titled “Synthese und Charakterisierung von Nanopartikeln: Anisotrope Edelmetall-Nanopartikel und Zinkoxid-Nanopartikel”, 2016, University of Duisburg-Essen, Germany. The obtained elongated silver particles were subsequently converted to tripropylene glycol monomethylether-based formulation according to example 10 in US20130270490 A1 (50% solids content).

The resulting silver particles were filtered off, washed with ethanol, dried and subjected to SEM analysis providing an average aspect ratio (AS) of 1.80:1 at a d₅₀ of 130 nm, and d₉₀ of 200 nm.

Example 1 (Ingredients: A, B, C, D, E)

0.361 g of Mowital B 45 H, dissolved in dipropylene glycol monomethyl ether (DPM) (17% solids content, product of Kuraray Europe GmbH, CAS-No. 68648-78-2) are metered into a container equipped with a stirrer. 0.013 g of Durazane® 1066 (product of Merck KGaA; CAS-No. 346577-55-7), 0.602 g of a paste of silver nano-sized particles (d₅₀ of 70 nm, d₉₀ of 115 nm, 50% solids content in tripropylene glycol monomethyl ether; cf. Example A) and 0.031 g of rhodium(III)-tris[2-ethylhexanoate] (2% in 2-ethylhexanol; product of American Elements) are subsequently added under stirring.

The resulting paste is applied onto a glass plate by means of a brush. The glass plate coated with the coating composition is then thermally treated at a temperature of 580° C. in air. The solvents evaporate and the organic compounds of the coating composition burn without remainings at this temperature. The resulting solid coating layer on the glass plate is composed of a glossy lower metallic layer of silver colour and an upper protective glass-like layer.

The layer is composed of 92.2% by weight of silver, 0.2% by weight of Rh and 7.6% by weight of SiO₂, based on the weight of the layer.

Example 2 (Ingredients A, B, C, D, E)

41% by weight of a solution of polyvinylbutyral binder (Mowital® B 45 H, product of Kuraray Europe GmbH, 10% by weight in propylene glycol monopropylether), are metered into a container equipped with a stirrer. 10% by weight of a silsesquioxane polymer preparation (MP 60LAN, product of Merck KGaA), 40% by weight of a paste of silver nanosized particles (d₅₀ of 70 nm, 45% solids in tripropylene glycol monomethyl ether; cf. Example A), 2% by weight of rhodium(III)-tris[2-ethylhexanoate] (product of American Elements), 2% by weight of bismuth(III)-tris[2-ethylhexanoate] (product of OMG Borchers GmbH) and 5% by weight of niobium(IV)-tetrakis[2-ethylhexanoate] (product of Strem Chemicals, Inc.) are subsequently added under stirring.

The resulting paste is applied onto a glass plate by means of a brush. The glass plate coated with the coating composition is then thermally treated at a temperature of 580° C. in air. The solvents evaporate and the organic compounds of the coating composition burn without remainings at this temperature. The resulting solid coating layer on the glass plate is composed of a glossy lower metallic layer of platinum white colour and a top coat glass-like layer.

The layer is composed of 60.1% by weight of silver, 26.7% by weight of SiO₂, 2.3% by weight of Bi₂O₃, 2.6% by weight of Nb₂O₅ and 8.3% by weight of Rh, based on the weight of the layer.

Example 3 (Ingredients: A, B, C, D, E)

14% by weight of polyurethane alkyd binder (Synolac® 8465×60, product of Arkema), dissolved in 33% by weight of propylene glycol monopropylether, are metered into a container equipped with a stirrer. 20% by weight of vinyltriethoxysilane (product of Alfa Aesar), 31% by weight of a paste of silver nanosized particles (d₅₀ of 70 nm, 50% solids in tripropylene glycol monomethylether; cf. Example A), and 2% by weight of rhodium(III)-tris[2-ethylhexanoate] (product of American Elements) are subsequently added under stirring.

The resulting paste is applied onto a glass plate by means of a brush. The glass plate coated with the coating composition is then thermally treated at a temperature of 580° C. in air. The solvents evaporate and the organic compounds of the coating composition burn without remainings at this temperature. The resulting solid coating layer on the glass plate is composed of a glossy lower metallic layer of yellow gold colour and a top coat glass-like layer.

The layer is composed of 68.6% by weight of silver, 27.9% by weight of SiO₂, and 3.5% by weight of Rh, based on the weight of the layer.

Example 4 (Ingredients: A, B, C, D, E)

32% by weight of polyurethane alkyd binder (Synolac® 8465×60, product of Arkema), and 5% by weight of silicone modified isophthalic acid alkyd resin based on linseed oil (Synolac® 5140×41, product of Arkema) are metered into a container equipped with a stirrer. 10% by weight of silicon tetrakis [2-ethylhexanoate] (product of Alfa Aesar), 50% by weight of a paste of silver nanosized particles (d₅₀ of 70 nm, 50% solids in tripropylene glycol monomethyl ether; cf. Example A), and 2% by weight of rhodium(III)-tris[2-ethylhexanoate] (product of American Elements) are subsequently added under stirring.

The resulting paste is applied onto a glass plate by means of direct screen printing. The glass plate coated with the coating composition is then thermally treated at a temperature of 500-620° C. in air. The solvents evaporate and the organic compounds of the coating composition burn without remainings at this temperature. The resulting solid coating layer on the glass plate is composed of a glossy lower metallic layer of yellow gold colour and a top coat glass-like layer.

The layer is composed of 85.4% by weight of silver, 11.2% by weight of SiO₂, and 3.4% by weight of Rh, based on the weight of the layer.

Example 5 (Ingredients A, B, C, D, E)

45% by weight of a solution of modified rosin resin (Dymerex™, product of Eastman Chemical Comp., 65% by weight in dipropylene glycol monomethylether), and 10% by weight of a silsesquioxane polymer preparation (MP 60LAN, product of Merck KGaA) are metered into a container equipped with a stirrer. 50% by weight of a paste of silver nanosized particles (d₅₀ of 70 nm, 50% solids in tripropylene glycol monomethylether; cf. Example A), 2% by weight of rhodium(III)-tris[2-ethylhexanoate] (product of American Elements), 2% by weight of bismuth(III)-tris[2-ethylhexanoate] (product of OMG Borchers GmbH) and 1% by weight of palladium resinate (MR4601-P; product of Wako Chemicals USA, Inc.) are subsequently added under stirring.

The resulting paste is applied onto a glass plate by means of decals (transfer paper). The glass plate coated with the coating composition is then thermally treated at a temperature of 500-620° C. in air. The solvents evaporate and the organic compounds of the coating composition burn without remainings at this temperature. The resulting solid coating layer on the glass plate is composed of a glossy lower metallic layer of platinum white colour and a top coat glass-like layer.

The layer is composed of 71.4% by weight of silver, 22.9% by weight of SiO₂, 2.3% by weight of Rh, 2.0% by weight of Bi₂O₃, and 1.4% by weight of Pd based on the weight of the layer.

Example 6 (Ingredients A, B, C, D, E)

45% by weight of a solution of modified rosin resin (Dymerex™, product of Eastman Chemical Comp., 65% by weight in dipropylene glycol monomethylether) are metered into a container equipped with a stirrer. 45% by weight of a paste of silver nanosized particles (d₅₀ of 70 nm, 50% solids in tripropylene glycol monomethylether; cf. Example A), 3% by weight of rhodium(III)-tris[2-ethylhexanoate] (product of American Elements), 2% by weight of bismuth(III)-tris[2-ethylhexanoate] (product of OMG Borchers GmbH) and 5% by weight of tetra-n-butyl germanium (product of Gelest, Inc.) are subsequently added under stirring.

The resulting paste is applied onto a glass plate by means of decals (transfer paper). The glass plate coated with the coating composition is then thermally treated at a temperature of 500-620° C. in air. The solvents evaporate and the organic compounds of the coating composition burn without remainings at this temperature. The resulting solid coating layer on the glass plate is composed of a glossy lower metallic layer of platinum white colour and a top coat glass-like layer.

The layer is composed of 81.6% by weight of silver, 11.6% by weight of GeO₂, 2.5% by weight of Bi₂O₃, 4.3% by weight of Rh, based on the weight of the layer.

Comparative Example 1 (Ingredients: A, C, D, E, H)

10 g of polyvinylpyrrolidone (PVP40; product of Sigma Aldrich) are dissolved in 80 g of ethanol. 50 g isobutanol, 5 drops of BYK® 065 defoamer (product of BYK Chemie GmbH) and 50 g of Ag₆₀Cu₃₀Sn₁₀ nano powder (product of American Elements) are added. The mixture is subjected to 30 min of ultrasonic wet milling to obtain a stable Dispersion A.

30 g of Dispersion A are mixed with 50 g of methylsilicone resin solution (Silres HK 46; 50% by weight methylsilicone resin in xylene/butanol 4/1; product of Wacker AG) and subjected to ultrasonic wet milling until a homogenous dispersion is obtained. The resulting paste is suitable for silkscreen printing on paper and plastic.

Comparative Example 2 (Ingredients: A, B, C, D, H)

15 g of polyvinylpyrrolidone (PVP40; product of Sigma Aldrich) are dissolved in 80 g of ethanol. 50 g isobutanol, 10 drops of BYK® 065 defoamer (product of BYK Chemie GmbH) and 50 g of Ag_(3.5)Sn_(96.5) nano powder (product of American Elements) are added. The mixture is subjected to 40 min of ultrasonic wet milling to obtain a stable Dispersion A.

A mixture of equal parts by weight of a silicone modified special fatty acid isophthalic alkyd resin (Synolac® 2700 WD 70; product of Arkema) and rosin resin is prepared via ultrasonic wet milling to obtain Mixture B.

Equal parts by weight of Dispersion A and Mixture B are mixed employing ultrasonic wet milling to obtain a paste for direct printing on glass.

Comparative Example 3 (Ingredients: A, B, C, D, H)

2 parts by weight of Niobium (IV)-2-ethyl hexanoate (product of Strem Chemicals, Inc.) are mixed with 8 parts by weight of rosin resin solution (60% by weight of resin in 40% by weight of isobutanol) to obtain Mixture C.

Equal parts by weight of Dispersion A from Comparative Example 2 and Mixture C are mixed employing ultrasonic wet milling to obtain a paste for direct printing on tiles. Thermal treatment is conducted at 700° C. in air. A bright yellow and shiny metal coating is obtained.

Comparative Example 4 (Ingredients: A, B, C, H)

50 g of Ag₆₀Cu₃₀Sn₁₀ nano powder (product of American Elements), 15 g of anionic surfactant (phosphate of ethoxylated C₁₂-C₁₅ aliphatic alcohol, Lanphos® TE 43; product of Lankem Ltd.) and 5 drops of BYK® 065 defoamer (product of BYK Chemie GmbH) are mixed with 100 g of xylene. The mixture is subjected to 30 min of ultrasonic wet milling to obtain a stable Dispersion A.

30 g of Dispersion A are mixed with 50 g of methylsilicone resin solution (Silres HK 46; 50% by weight methylsilicone resin in xylene/butanol 4/1;

product of Wacker AG) and subjected to ultrasonic wet milling until a homogenous dispersion is obtained. The resulting paste is suitable for silkscreen printing on paper and plastic.

Comparative Example 5 (ingredients: A, B, C, D, H)

50 g of Ag₃₅Sn₉₆₅ nano powder (product of American Elements), 15 g of anionic surfactant (phosphate of ethoxylated C₁₂-C₁₅ aliphatic alcohol, Lanphos® TE 43; product of Lankem Ltd.) and 10 drops of BYK® 065 defoamer (product of BYK Chemie GmbH) are mixed with 100 g of xylene. The mixture is subjected to 40 min of ultrasonic wet milling to obtain a stable Dispersion A.

A mixture of equal parts by weight of a silicone modified special fatty acid isophthalic alkyd resin (Synolac® 2700 WD 70; product of Arkema) and rosin resin is prepared via ultrasonic wet milling to obtain Mixture B. Equal parts by weight of Dispersion A and Mixture B are mixed employing ultrasonic wet milling to obtain a paste for direct printing on glass.

Comparative Example 6 (Ingredients A, B, C)

20 g of Ag nano powder of d₅₀ of 70-150 nm (product of American Elements) and 35 g of silicone-polyester resin (Silikoftal® HTL; product of Evonik Industries AG) are mixed with 55 g of dipropyleneglycol monomethyl ether. The mixture is subjected to 30 min of ultrasonic wet milling to obtain a stable dispersion for direct printing on paper, plastic, metal, glass or ceramic substrate. Thermal treatment is conducted at 150 to 600° C. depending upon the employed substrate.

Comparative Example 7 (Ingredients A, B, C, D, F)

20 g of Ag nano powder of d₅₀ of 70-150 nm (product of American Elements), 3 g of cobalt (II) bis [2-ethylhexanoate] (product of American Elements), 5 g of tetraethoxysilane (product of Merck KGaA) and 35 g of a linoleic based nitrocellulose alkyd resin (Synolac® 8026 X60; product of Arkema) are mixed with 37 g of dipropyleneglycol monomethylether. The mixture is subjected to 30 min of ultrasonic wet milling to obtain a stable dispersion for direct screen printing on glass employing 120T polyester mesh fabric. Drying is conducted for 2 h at 150° C. The obtained coating is furnished with a protective coating of silicone modified isophthalic acid alkyd resin based on linseed oil (Synolac® 5140 X41; product of Arkema) employing 120T polyester mesh fabric. Thermal treatment is conducted at 580° C.

Comparative Example 8 (Ingredients A, B, C, D; cf. WO 2012/059088 A2)

22.5 g of Ag nano powder of d₅₀ of 70-150 nm (product of American Elements), 15 g of silicon tetrakis [2-ethylhexanoate] (product of Alfa Aesar) and 30 g of a linoleic based nitrocellulose alkyd resin (Synolac® 8026 X60; product of Arkema) are mixed with 32.5 g of dipropyleneglycol monomethylether. The mixture is subjected to 30 min of ultrasonic wet milling to obtain a stable dispersion for direct screen printing on glass employing 120T polyester mesh fabric. Drying is conducted for 2 h at 150° C. The obtained coating is furnished with a protective coating of silicone modified isophthalic acid alkyd resin based on linseed oil (Synolac® 5140 X41; product of Arkema) employing 120T polyester mesh fabric. Thermal treatment is conducted at 550° C. to provide a yellow golden coating.

Comparative Example 9 (Ingredients: A, B, C, D, E)

The conditions and components described in Example 1 are used except for using a silver paste with particles described in Comparative Example B. The composition of the obtained layer matches the composition described in Example 1.

Example 8

Table 1 describes the performance of the various metal preparations and layers provided therefrom pursuant to the Examples and Comparative Examples.

Shelf life of metal preparations is determined by visual inspection in intervals of 1 month for a total period of 6 months. In the case of the formation of a serum or sedimentation of particles (segregation of phases) the test is stopped and shelf life is indicated as the month where no segregation is observed.

Scratch resistance is measured by scratching the layers with a water-wet Scotch-Brite™ flexible abrasive pad used for household cleaning. The layers are scratched without force 100 times. The result is evaluated visually on a scale of 1 to 5:

1: strong scratching/destruction of the layer,

5: no visual scratches.

Corrosion resistance is measured by subjecting the layers to an atmosphere of pure hydrogen sulfide in a sealed beaker for 1 day. The result is evaluated visually in comparison to a untreated layer on a scale of 1 to 5:

1: strong black coloration

5: no visual difference to the untreated layer.

Gloss is evaluated visually on a scale of 1 to 5:

1: little gloss, matte appearance

5: high gloss, silver mirror-like appearance.

TABLE 1 Performance of metal preparations and layers made therefrom Scratch Corrosion Aspect resistance resistance Gloss ratio Shelf life [arbitrary [arbitrary [arbitrary (AS) [months] units] units] units] Example 1 1.15:1 6 5 5 5 Example 2 1.25:1 6 4 4 5 Example 3 1.13:1 6 4 4 5 Example 4 1.13:1 6 4 5 5 Example 5 1.13:1 6 5 4 5 Example 6 1.13:1 5 5 5 5 Comp. Ex. 1 1.25:1 3 3 3 4 Comp. Ex. 2 1.19:1 4 4 2 4 Comp. Ex. 3 1.30:1 2 3 3 3 Comp. Ex. 4 1.25:1 1 4 3 5 Comp. Ex. 5 1.19:1 2 4 3 3 Comp. Ex. 6 1.30:1 4 3 2 5 Comp. Ex. 7 1.30:1 3 3 3 4 Comp. Ex. 8  1.8:1 3 5 4 3

Comparing Examples 1-6 with Comparative Examples 1-8 (where important components according to the present invention are omitted) one can clearly observe that shelf life of the Comparative formulations is significantly reduced and scratch resistance and/or corrosion resistance and/or gloss of the layers of the Comparative Examples are inferior to those of Examples 1-6.

Comparison of Example 1 with Comparative Example 8 reveals that shelf life of formulations bearing particles with an average aspect ratio of <1.5:1 and gloss of the resulting layers are higher than those of formulation bearing particles with an average aspect ratio of >1.5:1.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1:

Scanning micrographic 2-D projection of nano-sized silver particles (d₅₀=70 nm). A representative portion of such image is employed to determine the average aspect ratio (AS) of particles. 

1. Metal preparation comprising A) from 5 to 60% by weight of metal particles wherein said metal particles (i) exhibit a d₅₀ value, measured by the volume related laser diffraction method, in the range of from 30 to 300 nm, (ii) exhibit an average aspect ratio, measured by scanning electron microscopy or transmission electron spectroscopy, in the range of from 1.0 to 1.5, and (iii) are selected from Ag, Au, Ru, Ir, Pd, Pt, Cu Nb, or an alloy comprising at least one thereof, B) from 0.2 to 50% by weight of at least one organic compound of one or more elements selected from Si, Ge, B, P, Nb, Sn, Zn, Zr, Ti, Sb, Al, Bi, alkali metal or alkaline earth metal, C) from 10 to 85% by weight of a solvent, D) from 0.1 to 50% by weight of a polymeric binder, and E) from 0.01 to 30% by weight of at least one metal compound that is soluble in organic solvent, wherein the metal comprises at least one from Ag, Au, Ru, Ir, Pd, Pt, Os, and Rh, wherein the percentages are based on the total weight of the metal preparation.
 2. Metal preparation as claimed in claim 1, characterized in that the metal particles are noble metal particles selected from Ag, Au, Ru, Ir, Pd, Pt, or an alloy comprising at least one thereof.
 3. Metal preparation as claimed in claim 1, characterized in that the metal particles are of silver or a silver containing alloy having a silver content of at least 50% by weight, based on the weight of the alloy.
 4. Metal preparation as claimed in claim 1, characterized in that organic compound B is an alcoholate, carboxylate, citrate, acetylacetonate and/or tartrate of the elements selected from Si, Ge, B, P, Nb, Sn, Zn, Zr, Ti, Sb, Al, Bi, alkali metal and alkaline earth metal.
 5. Metal preparation as claimed in claim 1, characterized in that the Si containing organic compound is a silicon comprising polymer such as a polysilazane compound, a polysiloxane compound, a silicone resin, a silicone-modified alkyd resin, a silicone-polyester resin, and/or a silsesquioxane polymer.
 6. Metal preparation as claimed in claim 1, characterized in that solvent C is an organic solvent or a mixture of organic solvents, having a water content in the range of from 0 to at most 10% by weight, based on the total weight of the solvent: preferably wherein the solvent is selected from at least one of the group of alcohols, aromatic solvents, ketones, esters, ethers, ether-alcohols, saturated and unsaturated aliphatic hydrocarbons, or amides.
 7. (canceled)
 8. Metal preparation as claimed in claim 1, wherein the polymeric binder D comprises at least one of celluloses, polyamides, polyesters, polyethers, polyvinyls, polyacetals, polyvinylacetals, polysulfone, phenolic resin, ketone resin, epoxy resin, maleic resin and rosin resin.
 9. Metal preparation as claimed in claim 1, wherein metal compound E that is soluble in organic solvent at least one a resinate, a sulforesinate, a thiolate, a carboxylate or an alcoholate.
 10. Metal preparation as claimed in claim 1, further comprising, as ingredient F, from 0 to 5% by weight of at least one metal salt compound, wherein the metal comprises at least one from Co, Ni, Cu, Cr, Fe, and Mn: preferably characterized in that the metal salt compound is at least one from a resinate, a sulforesinate, a thiolate, a carboxylate or an alcoholate; or further comprising, as Ingredient G, from 0 to 10% by weight of a rheology modifying additive; preferably characterized in that rheology modifying additive G comprises at least one of the additives from pine oil, castor oil, a fatty acid, a fatty acid derivative, a natural or a synthetic wax; or further comprising, as ingredient H, from 0 to 10% by weight of a dispersant; preferably wherein dispersant H comprises at least one of polyacrylic acid, polyacrylates and their copolymers, polyurethanes polyvinylpyrrolidone, non-ionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants; or further comprising, as ingredient I, at least one additive. 11-16. (canceled)
 17. Process for the production of a metal preparation as claimed in claim 1, characterized in that the ingredients are intimately mixed with each other and a ready-to-use metal preparation is obtained; preferably characterized in that the mixing is carried out employing a rotor-stator-homogenizer, a triple-roll mill, or a Speedmixer®.
 18. (canceled)
 19. Gold, platinum, or silver colored decorative elements on articles exhibiting a surface, such as porcelain, china, bone china, ceramic, glass or enamel, comprising a metal preparation as claimed in claim
 1. 20. Solid coating on a substrate, comprising, based on the total weight of the solid coating, at least 60%, preferably at least 80%, by weight of metal particles of at least one metal selected from Ag, Au, Ru, Ir, Pd, Pt, Cu, No, or an alloy comprising at least one thereof, and further comprising at least 5% by weight, based on the total weight of the solid coating, of a glass matrix comprising at least one oxide of SiO₂, GeO₂, B₂O₃, P₄O₁₀, NbO₂, Nb₂O₃, SnO, SnO₂, ZnO, ZrO₂, TiO₂, Al₂O₃, Bi₂O₃, Sb₂O₃, alkali metal oxide, and/or alkaline earth metal oxide.
 21. Solid coating on a substrate as claimed in claim 20, characterized in that the metal particles are of silver or a silver comprising alloy having a silver content of at least 50% by weight, based on the total weight of the alloy.
 22. Solid coating on a substrate as claimed in claim 20, characterized in that the glass matrix additionally contains one or more metals or metal oxides, the metal(s) selected from Ni, Cu, Cr, Fe, Mn, Ag, Au, Rh, Ru, Ir, Pd, Os and Pt.
 23. Solid coating on a substrate as claimed in claim 20, comprising 5 to 40% by weight of the glass matrix, based on the total weight of the solid coating: preferably comprising from 10 to 30% by weight of the glass matrix, based on the total weight of the solid coating.
 24. (canceled)
 25. Solid coating on a substrate as claimed in claim 20, characterized in that the solid coating is composed of two layers lying on top of each other, wherein a first layer is located directly on the substrate and constitutes a densely packed metallic layer comprising aggregated metal particles, and wherein the second layer is located on top of the first layer and is a glass-like layer comprising at least one oxide of SiO₂, GeO₂, B₂O₃, P₄O₁₀, NbO₂, Nb₂O₃, SnO, SnO₂, ZnO, ZrO₂, TiO₂, A₂O₃, Bi₂O₃, Sb₂O₃, alkali metal oxide, and/or alkaline earth metal oxide.
 26. Solid coating on a substrate as claimed in claim 20, characterized in that the substrate is an article exhibiting an outer surface of porcelain, china bone china, ceramic, glass or enamel.
 27. Process for the production of a metal comprising coating on a substrate, characterized in that a metal preparation as claimed in claim 1 is applied onto a substrate and subsequently thermally treated at a temperature in the range of from 500° C. to 1250° C.
 28. Process as claimed in claim 27, characterized in that the substrate is an article exhibiting a silicatic surface, such as porcelain, china, bone china, ceramic, glass or enamel; or characterized in that the metal preparation is directly applied onto the substrate; or characterized in that the metal preparation is applied onto the substrate by means of a transfer medium pre-coated with the said metal preparation; or characterized in that the metal preparation is applied onto the substrate or transfer medium employing a printing process; preferably characterized in that the metal preparation is applied onto the substrate or transfer medium employing thermoplastic screen printing, ink jet printing, tampon printing, or offset printing. 29-32. (canceled)
 33. Process as claimed in claim 27, characterized in that the substrate coated with the metal preparation is partly or in total covered by an additional protective layer prior to thermally treating the coating. 